Electronic oscillator



Patented Feb. 14, 1939 ELECTRONIC OSCILLATOR Irving Wolff,Merchantville, N. J., assignor to Radio Corporation of America, acorporation of Delaware Application May 26, 1936, Serial No. 81,810

Claims.

My invention relates to electronic oscillators of the Barkhausen-Kurz ormagnetron type. More specifically, this invention relates to electronicoscillators in which the emission or mo- 5 tion of energy absorbingelectrons is reduced,

thereby increasing the efiiciency of the oscillatory currents.

It is well known to those skilled in that art that the term electronicoscillator is applied to electronic oscillatory devices in which theelectron transmit time is of the order of the duration of theoscillatory cycle. Such oscillators, operating on microwave lengths,develop relatively low power outputs. One of the reasons for the lowpower output is low efiiciency which is due, in part, to the emission ormovement of energy absorbing electrons. It is, therefore, one of theobjects of this invention to increase the efficiency of an electronicoscillator by controlling the emission or movement of electrons.

Another object is to prevent the emission of electrons, which absorbenergy from the oscillatory circuit. A still further object is to limitthe emission of electrons to such times at which the motion of theelectrons will be of proper phase to add to the energy in theoscillatory circuit. An additional object is to prevent the emission ormovement of energy absorbing electrons by creating a space charge, aboutthe cathode, which is controlled by the phases of the oscillatorycurrent.

In the accompanying figures,

Figure 1 is a schematic circuit diagram of my invention applied to aBarkhausen-Kurz oscillator,

Fig. 2 is a circuit diagram of the arrangement of Fig. 1 applied to amagnetron oscillator, and

Fig. 3 is a schematic diagram of a push-pull electronic oscillator withspace charge controlling means applied in accordance with my invention.

In Fig. 1 within an evacuated envelope I are suitably mounted a cathode3, a control electrode 5, an accelerating electrode 1 and an outerelectrode 9. The various electrodes may be coaxially arranged about thecathode; although my invention is not limited to any particulararrangement. The cathode 3 is connected through a pair of radiofrequency choke coils ll, I3 to a battery [5 or other suitable source ofenergy. The accelerating electrode 5 may be grounded and connectedthrough a radio frequency choke I! to the positive terminal of a biasingbattery [9. The negative terminal of the biasing battery is connected tothe cathode circuit.

A tuned circuit, which may be a transmission line comprising leads 2l-23, is connected to the cathode 3 and outer electrode 9, and a dipoleantenna 25. The dipole antenna is open circuited with respect to directcurrents, by the inclusion 5 of a blocking condenser 21. The outerelectrode 9 may be biased slightly negative with respect to the cathode3 by a battery 29 which is connected to the transmission line by radiofrequency choke coils 3|33. If the control electrode 5 and its circuit35 were omitted, the foregoing arrangement would operate as anelectronic oscillator in accordance with the accepted theory. That is,some of the electrons emitted by the cathode move through theaccelerating electrode and approach the outer electrode 9. Some of theseelectrons, upon approaching the outer electrode are repelled and proceedtoward the cathode. This cycle is repeated and, by virtue of the cloudof electrons moving between cathode and outer electrode, oscillatorycurrents are established in the tuned transmission line connected to thedipole antenna.

The operation of electronic oscillatory phenomenon has been explained asdue to the group-- ing of electrons, some of whose motions are of suchphase with respect to the generated voltage that they lose their energyof motion and thus deliver energy to an external circuit. Otherelectrons have a motion with respect to the generated voltage whichcauses them to be accelerated and thus abstract energy from the circuit.Fortunately, the former group of electrons exist in greater numbers andtherefore the electronic oscillations are persistent. However, if thelatter 35 group could be entirely suppressed or eliminated, theefficiency of an electronic oscillator would be greatly increased.

The first group, or electrons which give up energy, will be essentiallyin phase with oscillatory 40 current, and will be called in phaseelectrons. The latter group, or electrons which abstract energy, will beessentially out of phase with the oscillatory current and will be calledout of phase electrons. By means of the control electrode 5 which isserially connected through a phase adjusting circuit 31, bypasscapacitor 39, and adjustable contact M to the transmission line 2!, avarying voltage may be impressed on the control electrode of the properphase and 50 magnitude to prevent the emission of electrons with out ofphase motions.

' The control electrode may be given a steady initial bias by a battery43. I prefer to make the control electrode negative with respect tocathode. Since the control electrode establishes a space charge of theproper phase with respect to the currents in the oscillatory circuits,the space charge will tend to suppress the out of phase electrons.Likewise, the control electrode will establish a space charge in properphase to aid the movement of electrons which have a proper phase ofmotion with respect to the oscillatory currents. Thus these electronsgive up energy and thereby increase the operating efficiency.

In Fig. 2 a magnetron oscillator is shown. In most respects the circuitof Fig. 2 is essentially the same as the Barkhausen-Kurz oscillator ofFig. 1. Similar reference numerals have been used in this and the otherfigures to indicate similar elements. The accelerating electrode of theBarkhausen-Kurz oscillator is emitted and the outer electrode becomes ananode in the magnetron. A magnetic field is established by a permanentmagnet, an electro-magnet or a solenoid energized by a battery 41 asshown. The operation of the magnetron follows the normally acceptedtheory with the addition of the control electrode '5, which applies thephase controlling voltages as previously described in connection withFig. 1.

A push-pull Barkhausen-Kurz oscillator, similar to the single oscillatorof Fig. 1, is schematically illustrated in Fig. 3. The tuned or resonanttransmission line 2l--23 is connected between the pair of outerelectrodes. A second tunable transmission line 5| is connected betweenthe pair of cathodes 33. The bridging member 53 is adjustably arrangedto permit tuning of the transmission line 5|. The voltages forcontrolling the potential of the control electrodes 5-5 are determinedin this instance from taps 4| 0n the cathode tuned circuit 5|. Theseconnections or taps 4| could have been made to the transmission line 2 I23 connected to the anodes 9-9, inasmuch as voltages of the proper phasemay be derived from either tuned circuit. The final adjustment of thephase may be made by adjusting the effective length or reactance of thephasing circuits 31, 3?. The operation of the push-pull oscillator isessentially the same as the single oscillator of Fig. 1 with respect tothe control of electrons having an out of phase motion.

My invention is not limited to the precise arrangements of the severalillustrations which have been given by way of example. It should beunderstood that the push-pull oscillator may be applied to the magnetronas well as to the Barkhausen-Kurz oscillator. The connection from thecontrol electrode may be made to any part of the tuned circuit ortransmission line which may be connected between any suitablecombination of electrodes. The control electrode is not limited to usein thermionic tubes but may be applied in a similar manner to electronicoscillators whose cathode have photo-emissive or secondary electronicemissive properties.

I claim as my invention:

1. An electronic oscillator including in combination a tube having anelectron emitting cathode and a plurality of electrodes, a tuned circuitconnected between two of said electrodes, means for establishing anoscillatory current in. said tuned circuit, and means including anadditional electrode and a source of variable bias voltage obtained fromsaid tuned circuit and applied to said electrode for preventingelectrons having a motion in out of phase relationship with respect tosaid oscillatory current from absorbing energy from said current.

2. An electronic oscillator including in combination a thermionic tubehaving an electron emitting cathode, control electrode, acceleratingelectrode, and outer electrode, a tuned circuit connected between saidcathode and outer electrode, means for establishing oscillatory currentsin said tuned circuit and a connection from said control electrode tosaid tuned circuit for preventing the electrons having an out of phasemotion with respect to said oscillatory current from absorbing energyfrom said current.

3. A magnetron oscillator including a thermionic tube having an electronemitting cathode, a control electrode, and an anode, a tuned circuitconnected between said anode and cathode, means for establishingoscillatory currents in said tuned circuit including a magnetic field,and

a connection from said control electrode to said tuned circuit forpreventing the electrons having an out of phase motion with respect tosaid oscillatory currents from absorbing energy from said currents.

l. In a device of the character of claim 2,

means for adjusting the phase of the voltages impressed on said controlelectrode.

5. In a device of the character of claim 3, means for adjusting thephase of the voltages impressed on said control electrode.

6. A push-pull electronic oscillator comprising, in combination, a pairof thermionic tubes each having an electron emitting cathode and aplurality of electrodes, a tuned circuit connected between an electrodein each of said tubes, a second tuned circuit connected between saidcathodes,

means for establishing oscillatory currents in said tuned circuits, andmeans including an additional electrode and a source of variable biasvoltage obtained from said second tuned circuit and applied to saidelectrode for preventing electrons having out of phase motions withrespect to said oscillatory currents from absorbing energy from saidcurrents.

7. A push-pull electronic oscillator comprising, in combination, a pairof thermionic tubes, each of said tubes having an electron emittingcathode, a control electrode, an accelerating electrode, and an outerelectrode, a tuned circuit connected between said outer electrodes, asecond tuned circuit connected between said cathodes, means forestablishing oscillatory currents in said tuned circuits, means forderiving a voltage from one-of said tuned circuits, and means forimpressing said voltage on said control electrodes in proper phase toprevent electrons having out of phase motions with respect to saidoscillatory currents from absorbing energy from said currents.

8. In a device of the character of claim 7, means for adjusting thephase of the voltage impressed on said control electrodes.

9. In a device of the character described, means including a pluralityof electrodes for establishing electronic oscillations, a tuned circuitconnected between two of said electrodes whereby electronic oscillationsare established within a region within said means and within saidcircuit, and a connection between said tuned circuit and another of saidelectrodes whereby a variable bias voltage is derived from said tunedcircuit and applied to said other electrode for preventing the entry ofout of phase electrons Within said region.

10. In a device of the character described, means including a pluralityof electrodes for establishing electronic oscillations, a tuned circuitconnected between two of said electrodes whereby electronic oscillationsare established within a region within said means and within saidcircuit, a connection between said tuned circuit and another of saidelectrodes whereby a variable bias voltage is derived from said tunedcircuit, and means for adjusting the phase of said bias voltage andapplying said phase adjusted voltage to said other electrode forpreventing the entry of out of phase electrons within said region. 5

IRVING WOLFE.

